Apparatus for measuring mechanical power and/or torque



June 30, 1942. v w. c. HALL 2,237,796

' APPARATUS FOR MEASURING MECHANICAL POWER AND/OR TORQUE Filed Jan. 26,1940 2 SheetsSheet 1 mvsn'ron Wayne 6'. Hall A 1' TORNZ Y June 30,1942.4 w. c. HALL 2,287,796

APPARATUS FOR MEASURING MECHANICAL POWER AND/OR TORQUE Filed Jan. 26,1940 2 Sheets-Sheet 2 Vo/faye 01-0 0 Acmss 722% [I176 Va/Zaye mvsn-ronWayne 6. Hall BY n! AT TQRNI Y P tented June 30, 19 42 UN TE STAT EsPATENT. OFFICE I I APPARATUS FOR M ASURING MECHANICAL j rowan AND/RTORQUE Wayne 0. Hall, Washington, D. C. Application January 26, 1940,Serial No. 315,722.

(Granted under the act of March 3, 1883, as

- amended April 30, 1928; 370 0. G.-757) 6' Claims.

' rotative speed of the same, which measured quan- "titiesby subsequentcalculations give the mechanical power or torque transmitted. While avariety of electromechanical instrumentalities has been devised forgiving a continuousand direct reading of the transmittedshaft power ortorque'to thereby obviate the many disadvamnomical and compactapparatus.

nected across the remaining bridge diagonal.

The connection of the generator as aforesaid makes the provision of anyfurther voltage sources for power measurements unnecessary and thusresults in the production of a highly eco- For indicating the torqueunder transmission, an instrument is likewise employed in one bridgediagonal that will directly and continuously indicate a quantity which.is proportional to the torque of the, shaft, while a voltage that isindependent of the v shaft speed is'substituted for that of the gentagesand tedium of the above method, their use" has-been necessarilyrestricted principally because of their inherent complexity.

With a view to remedying the prior art deflciencies, I have devised anapparatus of the stated character that'gives a direct and continuousreading of either the transmitted shaft power or torque and which isrelatively simple and durable in structure. In carrying my inventioninto effect, I utilize, in combination with a power shaft, :1 spacedischarge device comprising an envelope enclosing at least threeelectrodes at least one of which is electron emissive and at least oneof which-is movable with respect tothe envelope. The envelope of thespace discharge device and at least the movable electrode thereof aresecured to the shaft at spaced points therealong in such a manner as tocausean increase in resistance between a plurality of the electrodessimultaneously with a decrease in a like resistance upon subjecting theshaft to a torsional deflection. The magnitude of this simultaneousvariation in the interelectrode' resistances is, therefore,approximately proportional to the torque being transmitted by the shaft.

The spacedischarge device is connected in a bridge circuit to form twobranches or arms thereof, which circuit is normally in a state ofbalance when no power or torque is being transmittedby the shaft. Whereit is desired to measure the mechanical power'under transmission, agenerator, the voltage output of which is proportional to the speed ofthe shaft. is utilized and is driven by the shaft at a speed equal to orproportional to that of the shaft. This generatoris connected across adiagonal of the bridge circuit while an electrical instrument fordirectly and continuously indicating a quantity that is proportional toboth the torque and speed of the shaft is conmust be maintainedsubstantially'constant alerator in the other bridge diagonal.

Where a qualitative indication of transmitted shaft power or torque isdesired, it is not necessary to maintain the emissivity of the electronemissive electrode of the space discharge device or the voltage acrossthe bridge diagonal that is independent of shaft speed constant. On theother hand, where a precision or quantitative indication of transmittedpower or torque is desired, the electron emissivity and voltag referredto though if the reading of the apparatus may be permitted to be inerror by a few percent, these quantitiesmay be allowed to vary from theestablished mean value by a few percent. Any

substantial deviation, however, in the constancy.

of these quantities from predetermined values will so effect thesensitivity of the indicating instrument acrossone of the bridgediagonals as to nullify any previous calibration of the ap- 'paratus.

For maintaininga substantially constant electron emissivity and asubstantially constant voltage across one diagonal of the bridge circuitwhen desired, I have devised a novel regulatory system for regulating afluctuating source of direct cur-- rent electromotive force which, whileof general application, may be advantageously utilized in the apparatusof the present invention. 'This regulatory system includes a fluctuatingsource of direct current electromotive force connected in circuit with aplurality of parallel branches and a branch across which it is desiredto maintain a substantially constant voltage drop. Means responsive toany current'change in one parallel branch attending any fluctuation inthe direct current electromotive force causes a substantially equal butopposite current change in the other parallel branch,'whereby thecurrent in the remaining circuit branch and hence the voltage dropthereacross is'mainta ined substantially constant. By connecting theelectron emissive electrode of the space discharge device in the latteror remaining circuit branch, it will be energized by a substantiallyconstant current at all times thus maintaining a substantially constantelectron emissivity. This latter circuit branch also provides asubstantially constant source of electromotive force forone diagonal ofthe bridge circuit when employing the apparatus for the measurement oftorque.

In the light of the foregoing, it is among the several objects of myinvention to provide an electromechanical apparatus that is relativelysimple and durable in structure for affording a direct and continuousreading of transmitted shaft power and/or torque; to provide anapparatus of the stated character that is economical and compact instructure and that is capable of giving either a qualitative or aquantitative indication of transmitted shaft power or torque; and toprovide a novel regulatory system of general application for use in thestated apparatus to insure quantitative or precision indications oftransmitted shaft power or torque.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying sheets of drawings wherein:

Fig. l discloses the preferred embodiment of the apparatus of myinvention for measuring transmitted shaft power and/or torque, showing,among other things, the space discharge device associated with the powershaft connected in the bridge circuit for forming two branches thereoftogether with the novel regulatory system;

Fig. 2 is an enlarged sectional view taken on the line 2-2 of Fig. 1showing in greater detail, among other things, the construction employedfor maintaining a concentric relationship between the shaft encirclingsleeves that engage the space discharge device;

Fig. 3 is the current-voltage characteristic of the ballast tube whichis included in one of the parallel branches of the regulatory systemshowing how the current in this branch varies in response to any changein the fluctuating source of direct current electromotive force; and

Fig. 4 is the current-voltage characteristic of that branch of theregulatory system across which it is desired to maintain a substantiallyconstant voltage drop showing how the current in this branch varies inresponse to any change in the fluctuating source of direct currentelectromotive force.

Before proceeding to a detailed description of the preferred embodimentof my-invention it is desired, among other things, to make certaingeneral remarks regarding'the space discharge device associated with thepower shaft so as to insure clarity in the subsequent exposition. Asnoted hereinbefore, this space discharge device comprises an envelopeenclosing at least three electrodes, at least one of which is electronemissive to thus serve as a cathode and at least one of which is movablewith respect to the envelope.

A cursory examination of Fig. l of the drawings will show that thecathode of the space discharge device associated with the power shafthas been depicted therein as of the thermionic type. the heating thereofto insure electron emission being accomplished directly by a suitablesource of electromotive force. I wish to emphasize in this connection,however, that I do not desire to be restricted to this type of cathodesince cathodes which emit electrons due to bombardment by rapidly movingions, electrons. or metastable atoms and are said to be secondarilyemissive, or photoelectric cathodes, or cold or non-thermionic cathodeswhich spontaneously emit electrons due to treatment thereof by aradio-active substance, all will serve the purpose of my invention. Asfor the thermionic cathode, it may be of the directly or indirectlyheated type and may be fabricated of a pure metal, be oxidecoated, be ofa metal provided with an adsorbed monatomic film of one of theelectro-positive metals or be of any other type known to the art.

The envelope of this space discharge device, which is fashioned from anyof the materials known to the prior art and serves to enclose theelectrodes, may be evacuated to produce a high vacuum and thus insure asubstantially pure electron discharge or may alternatively be providedwith a suitable filling of a gas or vapor, gases or vapors, or mixturesof gases and vapors at a selected pressure or pressures to insure thedesired operating characteristics.

It will be further noted from an examination of Fig. 1 of the drawingsthat the space discharge device associated with the power shaft is shownas incorporating twomovable anodes and a stationary cathode, the anodesbeing conjointly movable with respect to the envelope and the cathode inresponse to any torsional deflection of the shaft. The electrodearrangement employable in the present invention, however, is not to beunderstood as being restricted to the foregoing structure. It is onlynecessary that the envelope enclose at least three electrodes, at leastone of which is movable with respect to the en-- velope so that movementof at least the movable electrode will cause an increase in resistancebetween a plurality of electrodes simultaneously with a decrease in alike resistance. Any number of tube structures will satisfy theforegoing essential requirements and will readily suggest themselves tothose skilled in the art in the light of the teachings herein.

Finally, and of great importance, it is Essen tial that the meaning ofthe term "sensitivity" be understood as used with respect to theelectrical indicating instrument connected across one of the bridgediagonals. As here employed, the term sensitivity" designates theindication or incremental change in the reading of the instrument perunit deflection of the movable electrode of the space discharge device.The sensitivity of the indicating instrument is a function of theelectromotive force impressed across one of the bridge diagonals, aswell as a function of the emissivity of the cathode of the spacedischarge device associated with the power'shaft.

Turning now to Figs. 1 and 2 of the drawings, there is shown depictedtherein a rotatable shaft i having securely clamped thereto at spacedpoints 2 and 3 the sectionallzed sleeves 4 and 5, one of which exceedsthe other in length. The

set screws 6 and I are employed at the respecof the shaft intermediatethe points of securement of thesleeves thereto upon the application ofany torque will be transmitted to the. flanges 9 and iii of therespective sleeves 4 and 5 and cause them to be angularly displacedrelative to each other by the same amount.

A space discharge device identified in general by the referencecharacter H is shown, by way of example,as comprising an envelope l2enclosing a thermionic cathode l3 stationarily mounted with respect tothe envelope and interposed between a pair of conjointly movable anodesI4 and 15, the three electrodes being mounted for simultaneouscooperation and being disposed-t cause an increase in one anode-cathoderesistance simultaneously with a decrease in a like resist- 1 ance. Thetwo anodes l4 and I5 arerigidly secured to the elongated member or arml6 and are electrically insulated from each other and from the arin inany suitable manner. The arm,

- as shown, extends from the envelope interior to a point exteriorlythereof andat its point of emergence is flexibly and hermetically sealedto the envelope by employment of any of the wellunderstood expedientsknown to the prior art.

The envelope I2 of the space dischargedevice is suitably mounted on theflange ID of the sleeve 5, while the deflector arm l6 adjacent its outerextremity is laterally engaged by a series of set screws ll (Fig. 2)supported by.a bracket It securedto the flange 9 of the sleeve 4. Thus,it should be clear that any relative movement of the flanges 8 and", illattending any angular or torsional deflection of the shaft will causesimultaneously a decrease in spacing between the first anode and thecathode and an increase in spacing between the second anode and cathode,the

stituted by the two flxed resistors l9 and 20 and so much of thevariable balancing resistor 2! as may be included therein by appropriateadjustment of the sliding contact 22. It is thus evident that the bridgemay be initially balanced prior to any measuring operation by suitablemanipulation of the sliding contact 22 associated with the balancingresistor 2|. The variable resistor 23 under the control of the slidingcontact 24 is connected to the switch 26 by means of which the desiredelectromotive force is im pressed across one of the bridge diagonals. Byvarying the resistor 28, it is possible to vary slightly the voltageimpressed across the bridge diagonal 26-21 one end of which forconvenience is grounded; and hence to vary the sensitivity of theelectrical instrument or meter 28, which may be either or the voltage orcurrent type, connected across the remaining 'bridge diagonal ze -21'through the, double-pole double-throw reversing switch 29. The variableresistor 23 is usedprimarily to vary the sensitivity of the meter 28when employing the apparatus for the measurement of torque. Once.however, this resistor has been adjusted, the adjustment remains thesame for both power and torque measurements.

Itis. thus seen that the bridge circuit includes -iour arms or branches,two of which are constituted'by the resistances between the anode it,cathode l3 and anode l5, cathode 13 with the resistors l9 and 20 and somuch of the variable resistor 2i that may be respectively associatedtherewith constituting the remaining two branches.

Since only the space discharge device H is 86-, cured to and rotateswith the shaft I, provision must be made for electrically connecting thesame with the resistors l9 and 20 included imtwo of the branches of thebridge circuit and with suitable sources of electromotive force forenergizing. the bridge circuit and the thermionic cathode l3 of thespace discharge device. To this end slip rings 30, 3!, 32 and 33 areinsulatingly mounted from each other and from the shaft i to rotate withthe latter and cooperate respectively with brushes 30', 3|, 32' and 33'.By means of this arrangement, a continuous electrical connection isprovided between anodes l4, I5 and the respective resistors I9, 20through conductors 34, interconnecting anodes 14, I5 and slip rings 32,33; and conductors 34 35- interconnecting the brushes 32', 33' with theterminal portions 26, El of the respective resistors I9, 20. Thethermionic cathode i3 is maintained in continuous electrical connectionwith a suitable source of electromotive force which is preferably,

. although not necessarily, supplied by the regulatory system to bedescribed more in detail hereinafter. This interconnection is achievedby means of conductors 36 connecting the cathode and the slip rings 30and 3|; and the conductors variation in spacing-being directlyproportional V 36' interconnecting the brushes 30' and 3! with thecurrent mains 3i and 38 leadingto the regulatory system. As connected,the cathode it is energized by a substantially constant current toinsure a substantially constant electron emissivity.

A direct current generator 39, the voltage output of which isproportional to the shaft speed, is driven by the shaft I through a gear48 rigidly secured thereto which is in meshing engagement with a pinionM securely mounted on the armature shaft. Thus, the electromotive forcedeveloped at the generator terminals 42 is directly proportional to thespeed of the rotating power shaft which latter quantity may if desired,be

directly indicated by the standard type of voltmeter 43 calibrated inunits of speed and associated with the double-pole double-throw switch44 connected to the generator terminals M by means of the conductors 45.

The voltage developed at the generator tersistor t6 may be dispensedwith. The sensitivity of the indicating instrument 28 connected acrossthe bridge diagonal 26'--2'i is a linear function of the voltageimpressed across the bridge diagonal 26-2! only so long as this voltagedoes not cause near saturation current to flow in the space dischargedevice ll associated with the power shaft I. To prevent a voltage inexcess of this critical saturation voltage from being impressed acrossthe bridge diagonal 2E-zl at maximum shaft speed with the generatorhe'reemployed, the dropping resistor 46 is utilized.

This resistor insures that only the properv fraction of theelectromotive force at maximum shaftspeed is made available forsubsequent application to the bridge circuit.

A conductor 41 connects a suitable point along the length of thedropping resistor 48, which is always maintained at a positive potentialby the reversing switch 44, with the power contact 88 of the switch 28.The point of the dropping resistor 86 which is always maintained at anegative potential, as indicated, is connected by means of the conductor48 to the current main 38 which is grounded at 21. A switch 50, whenclosed, establishes electrical continuity along the length of theconductor 4! and may, if desired, be interlocked with the single-throwdouble-pole switch ii. The function of this latter switch, as will bepointed out more in detail hereinafter, is to make possible themeasurement of the saturation current of the space discharge device llassociated with the power shaft when this is desired. These interlockingswitches 50 and SI are so arranged that when one is closed the other isopen and vice versa. Normally, the single-pole single-throw switch 50remains closed and the double-pole switch 5| in consequence thereofopen. Thus, it should be clear that with the switch 58 closed and theswitch 28 thrown to engage the power contact 48 that a fixed fraction ofthe variable electromotive force of the generator 89 will be impressedacross the bridge diagonal 26--2'| and that the apparatus as connectedmay now be employed for the measurement of transmitted shaft power.

The operation of the apparatus for the measurement of mechanical powerwill now be described. With the switches 25 and 58 connected asaforesaid, the bridge is first balanced prior to any measuringoperation. Thus, with no power or torque being transmitted by the shaftI, the sliding contact 22 of the resistor 2| is manipulated in suchafashion that no differential voltage is developed across the diagonal28--2| of the bridge circuit when a suitable source of electromotiveforce is impressed across the remaining bridge diagonal 26-21.- Abalancing of the bridge circuit will be indicated by zero deflection ofthe instrument or meter 28 connected across the diagonal 28'--2I' of thebridge which develops a differential voltage attending the transmissionof any power or torque. The foregoing essential adjustment having beencarefully executed, the apparatus is now in condition for measuring orindicating the power transmitted by the shaft.

The power being transmitted by the shaft is proportional to the torqueand speed of the same. Thus, it should be clear that if the bridgecircuit is initially balanced prior to any power transmission that anydifferential voltage subsequently developed in the diagonal 26'2l' ofthe bridge circuit will be directly proportional to the transmittedtorque if it be assumed for purposes of exposition that the voltageimpressed across. 7

the bridge diagonal 252l and the emissivity of the cathode l3 of thespace discharge device are maintained substantially constant. On thebasis of this assumption, the sensitivit of the instrument 28, that isthe indication per unit deflection of the movable anodes l4 and IE, willremain constant and the magnitude of the meter indi cation or readingwill be proportional to the torque under transmission. Since, however,under conditions of power measurement the voltage impressed across thebridge diagonal 28-41 varies and is proportional to the speed of theshaft, the sensitivity of the indicating instrument 28 is not fixed butis a linear function of the shaft speed. Hence, the indication orreading of the meter will be proportional to both the torque and speedof the shaft and hence to the power being transmitted.

If the emissivity of the cathode l3 of the space discharge device II ismaintained substantially constant, the calibrated instrument 28 willgive a precision indication of a quantity that is proportional to boththe torque and speed of the shaft and hence to the power undertransmission. If, however, the emissivity is not maintainedsubstantially constant and varies within wide limits, the indication ofthe instrument 28 will only be qualitative in character and as such willenable the detection of the presence of any power under transmission orwill make known that more or less power is being transmitted. Anyconvenient unit of power may be used in calibrating the instrument; andthe calibration may be marked directly on the dial of the instrument ornoted on an accompanying chart. Thus, the instrument voltage droppingresistor 48 and to insure a proper reading of the instruments 28 and 43.The.connection of the generator 38 as above described makes theprovision of any further voltage source, other than that for energizingthe thermionic cathode, unnecessary and thus results in the productionof a highly economical and compact apparatus for the measurement ofmechanical power.

By throwing the switch 25 from its position of engagement with the powercontact 48 to a position of engagement with the torque contact 52, theapparatus is forthwith changed from a power measuring instrumentality toa device for measuring torque. Engagement of the switch 25 with thetorque contact 52 has the effect of disconnecting the variable generatorvoltage from the bridge circuit and of substituting therefor a voltagewhich may or may not have a substantially constantvalue but whose valuein any event .s definitely independent of the shaft speed. In thepreferred embodiment of the torque meter, the emissivity of the cathodeI8 of the space discharge device I I and the voltage impressed acrossthe bridge diagonal 26-2'l are maintained substantially constant. Theconnection of the cathode i3 is the same as that already described whenusing the apparatus for the measurement of power and may be such as toprovide either a variable or a substantially constant electronemissivity.

The engagement of the switch 25 with the torque contact 52 has theeffect of connecting the branch 53-21 of 'the regulatory system, acrosswhich there is maintained a substantially constant voltage drop, to thebridge circuit. Thus, there is maintained across the bridge diagonal2621 a substantially constant electromotive force. The foregoing is madepossible by virtue of the conductor 54 which connects the upper point orpoint of positive polarity 53 of the aforesaid regulatory branch withthe torque contact 52, a current meter 55 being in circuit with theconductor for a reason to be pointed out presently. The same meter 28connectedacross the bridge diagonal 26'21' may, if desired, be employedfor indicating a quantity that is proportional to the torque undertransmission.

The operation of the apparatus for the measurement of torque will now bedescribed. With the switch 25in engagement with the torque contact 52and the switch 50 closed, thus leaving the interlocked switch open, .thebridge is first 'balanced prior to any measuring operation.

Thus, with no torque being transmitted by the shaft, the sliding contact22 of the resistor 2| is manipulated in such a fashion that nodifferential voltage is developed across the diagonal 26'-2'| of thebridge circuit when a suitable electromotive force is impressed acrossthe remaining diagonal 28-21. The sensitivity of the instrument 28 isadjusted as desired by moving the sliding contact 24 to the proper pointalong the resistor 23. These adjustments having first been made, theapparatus is now in condition for measuring the transmitted torque.

- It should be clear from the foregoing that if a the bridge circuit isinitially balanced any differential voltage subsequently developed inthe diagonal 26'-21' of the bridge will be directly proportional to thetransmitted torque. If the emissivity of the cathode is of the spacedischarge device I I and thevoltage impressed upon the bridge circuitare maintained substantially constant, the calibrated instrument 28 willgive a precision indication of a quantity that is proportional to thetorque of the shaft. If, on the other hand, the emissivity and voltageare not maintained substantially constant but vary within wide limits,the indication of the instrument 28 will only be qualitative incharacter and as such will enable the detection of the presence of anytorque under transmission or that more or less torque is beingtransmitted without regard to its precise value; Any convenient unit oftorque may be used in calibrating the instrument 2B; and thecalibration, as in the case of the power meter, may be marked directlyon the instrument dial or noted on an accompanying chart. Thus, theinstrument 2! will directly and continuously indicate the torque beingtransmitt-ed by the shaft. If the direction of rotation of the powershaft should for any reason be reversed, it will be necessary to throwonly the double-pole double-throwswitch 29 into engagement with itsupper contacts to insure a v proper reading of the instrument 28.

In the preferred embodiment of my apparatus 3 for the measurement ofpower and/or torque, it

'is desired to maintain the [emissivity of the thermionic cathode ii ofthe space dischargedevice II substantially constant. The electronemissivity of the cathode is a function of its for checking theemissivity of the cathode and for restoring the same to its. initialvalue of emissivity when this becomes necessary. 1

Switch 5|, which is electrically connected to conductor It by theconductor 58. when closed connects the substantially constant source ofelectromotive force of the branch "-21 of the regulatory system directlyacross the space discharge device, thus causing saturation current toflow which isv a direct measurement of the emissivity of the cathode ii.The circuit thus completed by closure of the switch II extends from thejunction 53 of the regulatory system through the conductor 54', meter(which may 32', 33' by virtue of the conductors 34', 35' con-. nectedrespectively therewith. The circuit closed as aforesaid continuous fromthe slip rings 32, 33 to their respective anodes I, I5 through theconductors 34, 85 and from thence through the cathode l3, slip ring 30,brush 3!! and con ductor 36. to the remaining terminal 21 'of theregulatory branch. Thus, it should be clear that when the check switch5| is closed the effect-is to short circuit the bridge resistors l9 and20 and to causethe sum of the two plate currents of the space dischargedevice II or the saturation currents thereof to flow through themilliammeter 55.

Anychange in the emissivity of the thermionic cathode I 3 attending anychange in its surface condition may be compensated for by causing aslight variation in current through the cathode, the new current value,however, being maintained substantially constant by the regulatorysystem. This is accomplished by suitably adjusting a variable resistor51 in parallel with the cathode 13 through the sliding contact 68 inengagement therewith. By periodically checking the saturation current ofthe space discharge device H in the manner described above and by lmaintaining this current at all times substangizing the same with asubstantially constant I current furnished by the regulatory system. Itmay happen, howeventhat the surface condition of the thermionic cathode,becomes impaired during'the operating life of the space discharge devicethus necessitatinga slight increase or de crease in'temperature of thecathode to restore the initial and desired value of electron emissivity;This is accomplished by energizing the cathode with-aslightly higher orlower current, this new current value, however,,being likewisemaintained substantially constant by the regulatory. system." 7 To end;provision is made tially'constant, a substantially constant electronemissivity is insured.

For maintaining a substantially constant electron emissivity and asubstantially constant voltageacross one of the diagonals of the bridgecircuit when desired, I have devised a, novel regulatory system forregulating a fluctuating source of direct current electromotive forcewhich, while of general application, may be advantageously utilized inthe apparatus of the present invention.

This regulatory system includes a fluctuating source of direct currentelectromotive force connected in circuit with a'plurality of parallelbranches and a branch across which there is maintained a substantiallyconstant voltage drop by the regulatory action of thesystem. Meansresponsive to any current change inone parallel branch attending anyfluctuation in the direct current electromotive force causes asubstantially equal but opposite current change in theother parallelbranch, whereby the current in the remaining circuit branch and hencethe voltage drop thereacross is maintained substantially constant. Byconnecting the electron emissive electrode of the space discharge devicein the latter or remaining circuit branch it will be energized by asubstantially constant current at all times, thus maintaining itsemissivity substantially constant. This latter circuit .branch may alsoprovide a substantially constant source of electromotive force for onediagonal of the I bridge circuit when employing the apparatus for be amilliammeter) and switch ii to the brushes the measurement or torque ashas already been noted at length hereinbefore.

The first oi the parallel branches of the regulatory systemincludes aballast tube 59 in series with'the resistor 80. A resistor 61 may, ifdesired, be shunted across the ballast tube 59 to increase the currentoutput of the shunted combination over that of the tube alone. Theballast tube 59 may be any conventional prior art tube and is shownhere, by way of example, as including an envelope with a gaseous fillingof hydrogen in which there is enclosed a ballast resistor 62 fabricatedof iron wire connectible with the'positive terminal of the fluctuatingsource of direct current electromotive force by closure of the switch63.

The current voltage characteristic of the ballast tube 59 depicted inFig. 3 of the drawings shows how the total current Ii in the parallelbranch described in the preceding paragraph varies in response to anyvoltage change in the non-linear portion of the i i-e; characteristic'atzero plate current which is not permissible if the conditions abovenoted are to be met. Therefore, even when the ballast tube is passingits maximum current a small current is passing through each of the tubes84. The total quiescent current in the second parallel branch flowingtofluctuating source of direct current electromotive force It will benoted that within a limited range of voltage variation of the directcurrent source of electromotive force, that the current variation in theparallel branch is substantially linearly related to the varying voltagedrop across the ballast tube and that this substantially linear currentvariation is from Ii to 11" where I1 for convenience of exposition, maybe taken as the quiescent value of current about which the currentfluctuations or incremental current changes A11 occur. Such a largecurrent variation is not permissible where precision measurements are tobe made with the power and/or torque meter since, among other things,wide changes in electron emissivity would ensue.

The second of the parallel branches includes one or'more shunt connectedtubes or space discharge devices which operate essentially as triodes. Ihave shown. by way of example, four RCA Type-48 tubes identified ingeneral by the reference character 64 in which the screen grids are tiedback to their respective anodes in each instance so that the tubes mayoperate as triodes. While any conventional prior art triode may beemployed, this type of tube was chosen because of its ability to deliverlarge power at relatively low plate voltages.

The screen grids 65 tied to the anodes 65 are connected in shunt and toa terminal 61 of the first parallel branch by means of the conductor 68;while the indirectly heated cathodes 69 energized by the heater elements10 are likewise shunt connected and by the conductor 1| are electricallyconnected to the remaining terminal 53 of the first parallel branch. Thecontrol grids 12 of the tubes 64 are also connected in shunt and havetheir grid circuits completed in a manner to be described more in detailhereinafter.

It is to be emphasized that the triodes 64 must at all times be operatedsubstantially on the linear portions of their ir-eg characteristic andthat the control grids 12 must never swing positive with respect totheir cathodes 69 so as to prevent any disturbance in the voltagerelationships of the system. From the foregoing, it follows that anycurrent change in the second of the parallel branches will be linearlyrelated to any voltage change on the control grids 12 and that thisbranch current may by suitable ad- Justment have the desiredcompensating effect on the linearly varying current of the firstparallel branch. I

Thus, the number of tubes in the second paralward the Junction point 53is designated 1: and corresponds to the similarly flowing quiescentcurrent ll of the first parallel branch.

The'circuit branch across which it is desired to maintain asubstantially constant voltage drop and hence a constant current flowtherethrough extends from the junction point 58 to the grounded point21. This latter junction point, it will be observed, is connected to thenegative terminal of the fluctuating source of direct currentelectromotive force by the conductor 18. Thus, it should be clear thatin the regulatory system of the present invention a fluctuating sourceof di- 'rect current electromotive force is connected in I the tubes 84and the control tube 1|. The energization oi the heater elements 10 and11 in the manner noted is of great importance since it insures asubstantially constant electron emissivity of the cathodes in the tubesin question and hence a high degree of stability of the regulatorysystem. The resistor 15 is used to obtain the desired voltage dropacross the constant voltage branch 53-21. A voltmeter 19 connectedacross the constant voltage branch indicates by a substantially constantreading that the system is operating as desired. The total current inthe constant current branch flowing away from the junction point 53 isdesignated 1:.

In accordance with the present invention, the current I; in the branch"-21 is maintained substantially constant attending a limited variationin the voltage of the fluctuating source of direct current electromotiveforce. This is achieved by causing a substantially equal but oppositecurrent change in the second parallel branch simultaneously with and inresponse to a current change in the first parallel branch. Thus, beforeany current change takes place in the first parallel branch, anapplication of Kirchhoffs first law relating to networks at the junctionpoint 53 gives the following equation:

I1+I2=I3 Eq. (1)

After an incremental change of current AIl in the first parallel branchattending a voltage fluctuation in the source of direct currentelectromotive force, the equation now applicable at the junction point51 will be since as postulated the accompanying incremental change incurrent of the second parallel branch, namely, AI: must at all times beequal in magnitude to Ah but opposite in sign. Thus, the

current 13 in the branch 53-41 and hence the voltage thereacross ismaintained substantially constant within a limited range of voltagevariation of the fluctuating source of direct current electromotiveforce, as clearly indicated in Fig.

4 of the drawings.

While the voltage across branch 53-27 is maintained substantiallyconstant since the current therethrough and the equivalent resistancethere-' of are constant, the voltage across the series resistor 60 inthe firstparallei branch will vary attending any fluctuation of thecurrent therein. This voltage variation across the resistor itoccasionedby a current change in the first parallel branch provides theexcitation for the control tube It of the voltage amplifier throughwhich the proper voltages are applied-to the grids it of the tubes 66 tocause, a substantially equal but opposite current changein the secondparallel branch. Thus, the desired regulation is achieved;

factor, I wish to emphasize in this connectionthat any conventionalprior art triode may be used instead. A high amplification factor makespossible a low voltage excitation and hence a small value for the seriesresistor to in the first parallel branch. Hence, it may be said that thehigher the amplification factor ofthetube ill,

the smaller maybe the magnitude of the series resistor til. In someinstances, where this is desirable, the resistor it may even be omitted.Where omitted, however, the regulation will not whence the circuit iscompleted through the cathodes 89 and the conductor H to the initialjunction point 53. The point 93 of the series resistor 60 to which theconductor 94 issecured is preferably chosen to give the best value ofplate potential for the control tube 18. To have raised' the platepotential of this tube excessively would have resulted in raising themean potentials of the grids ll of the tubes 84 to a point where aprohibitive positive grid swing might ensue under certain operatingconditions. On the other hand, to have excessively lowered the plate,potential of the tube 18 would have need lessly-reducedthe amplificationof thevoltage amplifier. In operation, the main control switch 83 of thregulatory system is closed, and the sliding contact it oi thepotentiometer is adjusted until the voltmeter itrecords a substantiallyconstant voltage attending any nuctuatlonin. the voltage of the directcurrent source or electromotive force. Under these circumstances, thedesiredv current and voltage regulation in the branch 53-2? of thesystem is obtained. That this is so should be evident irom the followingdiscussion.

By adjustment of the sliding contact at of the potentiometer in themanner-above noted, the

needed portion oi the variable voltage across the series resistor-db ofthe first parallel branch attending any current change therein isselected. This incremental change in voltage provides the posit-e insign to A11, thus maintaining the conbe as critical as that depicted inFig. 4' of the.

drawings'but will be a vast improvement over that obtainable with aballast tube alone.

A high ohmic resistor to, which draws negligible current, is connectedto a suitable point bl voltage 89 for the control grid 82. This biasingvoltage 89 is oi such a value as to maintain the control grid 82 in itsvoltage excursions at all times negative with respect to the cathode blso as to insure substantially distortionless amplification and thepreservation of the desired voltage-relationships within the. system. il

A load resistor it of suitable value has one terminal ill connected tothe anode d0 of the tube it and to the grids T2 of the tubes at whilethe remaining terminal 92 thereof is connected to the screen'grid d3 ofthe tube I8 and to a suitable point it. along the seriesi'esistor it.

Thus, the grid circuit of each of the tubes 6d extends from the junctionpoint 53 through the series resistor til to the junction point as andfrom thence by means of the conductor at to the terminal 92 oi the loadresistor-db; and from the remaining terminal 3 it of this resistorthrough the conductor at to the grids it from excitation for the controlgrid er of the tube it and in amplified form appears across the loadresistor ht. This amplified incremental voltage is of such a value as tochange the voltage applied to the grids E2 of the tubes at in a mannersuch that Ala will be equal in magnitude but opstancy of Is in thebranch bl-tl all in a manner pointed out hereinbefore.

More specifically, an increase of current A11 in the first parallelbranch will cause the grid 82 of the control tube is to become lessnegative by a certain amount with respect to its cathode 8|. This causesan increase in platecurrent through thetube "ill and hence an increasein voltage drop through the load resistor as. Since. however, thecontrol grids it of the tubes 6% are connected to the terminal 9| of theload resistor '96 by means oithe conductor 95, this increase in voltagedrop has the effect of causing these grids to become more negative withrespect to their cathodes it. The swing of the individual grids 12,however, is only great enough to cause a decrease of A712 in the totalcurrent of the sec-' Thus, the desired regulation is achieved. That adecrease in current in the first parallel branch will through thevoltage drop in the series resistorv 61B, the-associated control tube itand load resistortll cause an increase in current of the I samemagnitude in the second parallel branch .believed to be evident.

made foren- It is desirable that provision be ergizing the cathode it ofthe space discharge device H only after the regulatory system hasattained stability so as to avoid any possible impairment of the cathodedue to excessive current energization.-- While this may be achievedmanually by simply shorting out the cathode for a predetermined timethrough suitable circuit con-- nections, I have devised means for,automatically achieving the foregoing-J A switch at under the conductors99 and Irespectively, short circuits the cathode I3 thus preventing anypassage of current therethrough. Any convenient means may be employedfor energizing the solenoid 91 when theregulatory system has attainedstability, which in consequence of the energization has the effect ofopening the switch 96 and thus permitting current flow through thecathode I3 of the space discharge device I I so long as the main controlswitch 63 of the regulatory system is closed.

I have illustrated, by way of example, an instrumentality identified ingeneral by the reference character IOI for achieving the desiredenergization of the solenoid 91. This insti'umentality is connectedacross the source of direct current electromotive force by means of theconductors I02 and I03 in the manner shown and is set in operation bythe closure of the main circuit switch 63. In its initial andunenergized state, the movable contact I04 of the current bow I05engages the fixed current contact I06; and the movable solenoid contactI0I is in engagement with the fixed contact I08of the heating resistorI00 cooperating with current bow I05. Upon closure of the switch 63, aheating circuit is completed from the positive terminal of the source ofelectromotive force through the conductors I03 and H0 to the movablesolenoidcontact I01 and from thence through the fixed contact II3 to.one side of the current bow I05. The circuit continues through thecurrent bow I05, movable contact I04, fixed contact I06, and conductorIll to one side of the solenoid 01 and from thence through the solenoidand conductor I00 to the conductor 73 which is connected to the negativeand remaining terminal of the voltage source.

Thus, after a predetermined time interval has elapsed subsequent to theclosure of the maincontrol switch 63, the solenoid 91 is energized. Theregulatory system having by this time attained stability, theenergization of the solenoid 91 causes an opening of'the switch 96 withthe result that the cathode I3 of the space discharge device II is nowenergized. The time delay in the energization of the cathode is entirelyautomatic and energization occurs only after the regulatory system hasattained stability so that any possibility of.damage to the cathode iseffectively avoided.

According to the provisions of the patent statutes, I have set forth theprinciple and mode of operation ,of my invention. and have illustratedand described what I now consider to represent its best embodiment.However, I desire to have it understood that within the scope of theappended-claims the invention may be practiced through the solenoid I I2which extends from the I05, solenoid Land conductor I02 to the megativesource terminal with the result that the movable solenoid contact I01 ismoved from engagement with its fixed contact I08 to cause aninterruption of the heating circuit heretofore described and intoengagement with a second fixed contact II3 By engagement of the movablesolenoid contact I 01 with the contact I I3, 9. holding circuit for themovable contact I0I-is completed from the positive terminal of thesource of electromotive force through the conductors I03 and II 0 to themovable contact I01 and h from thence through the fixed contact II3,solenoid H2 and conductor I02 to the other terminal of the voltagesource. This holding circuit is maintained so long as themain controlswitch 63 is closed.

' As the heating circuit hereinbefore described has now beeninterrupted, the movable contact I04 of the current bow I05 graduallymoves from. engagement with its fixed contact III back toward the fixedcontact I06; Upon engagement with the fixed contact I08 the energizingcircuit for the solenoid 91 is completed. --'I'his circuit extends fromthe positive terminal of the source of electromotive force through theconductors securing said envelope and at least the movable electrode tosaid shaft at spaced points therealong to thereby cause an increase inresistance between a plurality of electrodes simultaneously with adecrease in a like resistance upon subjecting the shaft to torsion, abridge circuit in which the space discharge device is connected to formtwo branches thereof, a generator driven by said shaft and an instrumentfor indicating a quantity that is proportional to both the torque I03,IIO, movable solenoid contact I01 andilxed .is electron emissive andatleast one of whichis movable with respect to the envelope, means forsecuring said envelope and at least the movable electrode to said shaftat spaced pointstherealong to thereby cause an increase in resistancebetween a plurality of electrodes simultaneously with a decrease in alike resistance upon subjecting the shaft to torsion, a bridge circuitin which the space discharge device is connected to form two branchesthereof, a substantially constant source of electromotive force,a'generator driven by said shaftand an instrument for indicating aquantity that is proportional to the torque or to both the torque andspeed of the shaft, the instrument-being connected across adiagonal ofthe bridge circuit and means for connecting either the source ofelectromotive force or the generator securing said envelope and at leastthe movable electrode to said shaft at spaced points therealong tothereby cause an increase in resistance between a plurality ofelectrodes simultaneously with a decrease in a likeresistance uponsubjecting the shaft to torsion, a bridge circuit in which the spacedischarge device is connected to form two branches thereof, a generatordriven by said shaft and an instrument for indicating a quantity that isproportional to both the torque and speed of the shaft, the outputterminals of said generatorbeing connected across a diagonal of thebridge circuit and the instrument being connected across the remainingdiagonal thereof,

a regulatory system including a fluctuating source of direct currentelectromotive force and a plurality of parallel branches connected incircuit with the aforesaid source and the electron emissive electrode ofthe said space discharge device, and means responsive to any currentchange in one parallel branch attending any fiuctuationin the saidelectromotive force for causing a substantially equal but oppositecurrent change in the other parallel branch, .whereby the currentenergizing the electron emissive electrode is maintained substantiallyconstant. ,1

4. In combination with a power shaft a space discharge device comprisingan envelope enclosbetween a plurality of electrodes simultaneously witha decrease in' a like resistance upon subjecting the shaft to torsion, abridge circuit in which the space discharge device is connected Ito formtwo branches thereof, a generator driven by said shaft and an instrumentfor indicating aquantity that is proportional to both the torque andspeed of the shaft the output terminals of said generator beingconnected across a diagonal of the bridge circuit and the instrumentbeing connected acrossthe remaining diagonal thereof, a regulatorysystem'including' a fluctuating source of direct current electromotiveforce and a plurality of parallel branches connected in circuit with theaforesaid source and the electron emissive eleccharge device conprisingan envelope enclosing at least three electrodes, at least one of whichis electron emissive and at least one of which is movable with respectto the envelope, means for securing said envelope and at least themovable electrode to said shaft at spaced points therealong to therebycause andncrease in resistance between a plurality of electrodessimultaneously with a decrease in a like. resistance upon subjecting theehaft to torsion, a bridge circuit in which the space 'discharge deviceis connected to form ,two branches thereof, a substantially constantsource of electromoiive force and an instrument for indicating aquantity that is proportional to the torque of the shaft, the saidsource of electromotive force being connected across a diagonal of thebridge circuit and the instrument being connected across the remainingdiagonal thereof, a regulatory system including a fluctuating source ofdirect current electromotive force and a plurality of parallel branchesconnected in circuit with the aforesaid fluctuating source and theelectron emissive elec trode of the said space discharge device, andmeans responsive to any current change in one parallel branch attendingany fluctuation in the said electromotive force for causing asubstantially equal but opposite current change in the other parallelbranch, whereby the current energizing the electron emissive electrodeismaintained substantially constant.

'6. In combina ion-with a shaft a space discharge device comprising anenvelope enclosing at least three electrodes, at least'one of which iselectron emissive and at least ne of which is movable with respectto theenvelope, means for securing said envelope and at least the movtrode ofthe said space discharge device, means responsive to any current changein one parallel branch attending any fluctuation in thesaidelectromotive force for causing a substantially equal but oppositecurrent change in. the other parallel branch, whereby the currentenergizing the electron emissive electrode is maintained substantialableelectrode to said shaft at spaced points therealong to thereby cause anincrease in resistance between a plurality of electrodes simultaneouslywith a decrease in a like resistance uponsubjecting theshaft to torsion,a bridge circuit in which the space discharge device is connected toform two branches thereof, a substantially constant source ofelectromotive force and an instrument for indicating a quantity that isproportional to the torque of the shaft,'the said source ofelectromotive force being connected across a diagonal of the bridgecircuit electromotive force and a plurality of parallel branchesconnected in circuit with the aforesaid fluctuating source and theelectron emissive electrode of the said space discharge device, meansresponsive to any current change in one parallel branch attending anyfluctuation in the said electromotive force for causing a substantiallyequal but opposite current change in the other parallel branch, wherebythe current energizing the electron emissive electrode is maintainedsubstantially constant, and means for delaying the energization .of theelectron emissive electrode upon closure of the regulatory system.'

WAYNE c.

